The present invention is directed to a high conductivity grounding tape used in connection with garments worn in so-called "clean rooms".
It is well recognized in the industry that in the manufacture of certain sensitive electronic components i.e. "chips", that even low voltage charges can permanently damage the chips at certain stages of their manufacture. By way of example, operators of manufacturing equipment can produce several hundred volts of static electricity merely by minor movements of their arms.
In order to dissipate voltages as low as those noted, it is imperative that the grounding, voltage dissipating conductor have a high conductivity factor.
While a pure wire conductor will provide the requisite low resistance, it is desirable, and in most instances imperative that the grounding conductor exhibit the "hand" or feel of a conventional fabric.
Numerous attempts have been made to create a fabric-like tape which will exhibit the necessary high conductivity and "hand" demanded by industry and which also will maintain these characteristic through multiple laundering cycles. By way of example, clean room, static dissipating garments are expected to be capable of withstanding a hundred or more washings in deionized and hence highly reactive water, without material increase in the resistance of the grounding tape.
Attempts to provide a tape having the above desired characteristics have included incorporating in the fabric metal clad polymer yarns i.e. yarns coated with silver, copper, etc. The tapes fabricated from clad yarns fail to satisfy the laundering requirements since the ohmic resistance exhibited increases progressively from washing to washing.
Tapes have been formed of yarns impregnated with conductive materials such as carbon. However, carbon filled yarns possess an electrical resistance thousands of times greater than that required in many "clean room" environments.